Intravascular medical procedures allow the performance of therapeutic treatments in a variety of locations within a patient's body while requiring only relatively small access incisions. An intravascular procedure may, for example, eliminate the need for open-heart surgery, reducing risks, costs, and time associated with an open-heart procedure. Intravascular procedures can also enable faster recovery times with lower associated costs and risks of complication.
An example of an intravascular procedure that significantly reduces procedure and recovery time and cost over conventional open surgery is a heart valve replacement or repair procedure. An artificial valve is guided to the heart through the patient's vasculature. For example, a catheter is inserted into the patient's vasculature and directed to the inferior vena cava. The catheter is then urged through the inferior vena cava toward the heart by applying force longitudinally to the catheter. Upon entering the heart from the inferior vena cava, the catheter enters the right atrium. The distal end of the catheter may be deflected by one or more deflecting mechanisms, which can be achieved by tension cable, or other mechanisms positioned inside the catheter. Precise control of the distal end of the catheter allows for more reliable and faster positioning of a medical device and/or implant and other improvements in the procedures.
An intravascularly delivered device needs to be placed precisely to ensure a correct positioning of the medical device, which is essential for its functionality, as the device may be difficult to reposition after the device is fully deployed from the delivery system. Additionally, the ability to recapture a partially deployed device is desirable in the event that the distal end of the catheter moves relative to the target location and compromises the precise positioning of the device.
The expansion and/or recapture of the device requires the collapse of one or more movable portions of the device. The one or more movable portions expand and/or collapse toward the longitudinal axis of a sheath during longitudinal movement of the sheath over the transverse exterior of the device. Proximal movement of the sheath relative to the device allows the device to expand beyond a diameter of the sheath. Distal movement of the sheath relative to the device constrains the device in the tip of the sheath. More rigid and/or robust devices with a high outwards force require a stiffer sheath and/or greater longitudinal forces to move the sheath relative to the device. Increasing the stiffness of the sheath is undesirable during intravascular procedures since a stiff sheath might not be able to be delivered through a tortuous anatomy.